Aerial cable support



,NOV- 8? 1938. E. c. vRooMAN 2,136,258

AERIAL CABLE 'SUPPORT Filed om. 15, 195s l-i is AtfCcww'wegl Patented Nov. 8, 11938 UNITED STATES AERIAL CABLE SUPPORT Edward C. Vrooman, to Locke Insulator a. corporation of Maryl Application October 15,

Schenectady, N. Y., assigner Corporation, Baltimore, Md.,

an y

1936, Serial No. 105,705

5 claims. (cl. 17a- 251) The present invention relates to supports for cable of the type having one or more insulated conductors carrying current at full line potential and a surrounding' conductor carrying current generally but not always at ground potential, the latter conductor comprising alternate hard wires, such as steel, and soft wires, such as tinned copper or aluminum, arranged to form an annulus. In addition to carrying current, the outer conductor also acts as an armor. On account of the high tensile strength of the steel wires, it is practical to use long spans with a corresponding reduction in the number of supporting poles. The supporting of such a cable on the poles and at its ends introduces certain problems which are not present with usual types of cable. With the long spans made possible by the cable construction, it has been found that the insulation on the center conductor or conductors is or may be injured at the point where the supports are located. This injury appears in the form of crushed or flattened insulation with the result of decreasing its effectiveness.

The object ofmy invention is the provision of an improved means oi'simple construction for supporting cables of the character described which will securely support them in place and this without injury to the parts thereof and specifically to the insulation.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and claims appended thereto.

In the drawing, which is illustrative of my invention, Fig. 1 is a view of a cable end which is partially prepared for anchoring; Fig. 2 is a similar view showing a further step in the operation; Fig. 3 shows the upper end of a supporting pole with the cable anchored thereto; Fig. 4 is a view illustrating the arrangement of the insulated center conductor and the end support or anchor-- ing means; Fig. 5 is a view of one of the clamps; Fig. 6 is a view in cross-section of the cable on an enlarged scale, and Fig. 7 is a detail view showing a tap arranged between cable supporting poles.

Referring rst to Fig. 6, 'l indicates the center conductor of which more than one may be provided. The conductors may be solid or stranded as usual. Surrounding the conductor is a re1atively thick covering of insulation 8 of which rubber or a rubber-like compound is an illustration. The outer conductor which generally operates at ground potential comprises round steel wires 9 of high tensile strength which are substantially free of torsional strains, and wires I0 of tinned soft copper or aluminum of good electrical conductivity. The latter wires are initially of rectangular cross-section and occupy radial positions which means that they have to be slightly twisted in forming the cable because both wires 9 and l0 are applied over the insulation with a long pitch spiral. By externally applied compression pressure, the hard Wires are forced into the soft wires to form seats in the side walls thereof. As a result, the wires are interlocked and form a self-supporting structure or annulus. My invention, however, is not limited to the particular way in which the cable is made.

In order to support or anchor the cable, a band Il which may be of wire is applied to-the cable at a suitable distance from the cut end thereof. The band is used to limit the spreading of the wires 9 and lll which is done by hand, the wires s being bent outwardly one at a time until they occupy'the approximate positions illustrated in Fig. l. In practice, the wires are desirably bent outward to an angle of about 45. Ii they are bent outwardly too far, they have a tendency to kink which would make it more dicult to as# semble them about the supporting tube, to be referred to later. This spreading of the wires exposes the insulation 8 on the center conductor. In order to prevent corona effect, especially in the region adjacent the temporary band l l, a thin metal wrapping l2, such as copper tape, is snugly applied, and desirably with overlapping turns. The shielding tape is preferably long enough so as to protect the connected parts of the center wire as will appear later. It may be prevented from unwinding by a few turns of adhesive tape. The next step is to slip a sleeve or tube I3, as of brass for example, over the copper tape or electrostatic shield and insulation on the center conductor, the upper end of which is reasonably close to the band Il. The tube may temporarily be held in place by winding a few turns of adhesive tape over one end ,of it and also over a part of the insulation 8 or shield or both. The steel wires 9 are then laid spirally one after the other over the tube I3 as shown in Fig. 2. It will be found that these wires will smoothly lie over the tube and assume very nearly the same positions they occupied in the cable itself. The lower ends of the wires as they are applied may be held by one hand while the other is used to properly spiral and position the wires. After the wires are applied, they may be temporarily bound with adhesive tape. After the wires are properly positioned, they 'are secured around the tube by clamps I4 such for example as shown in Fig. 5. My invention is not, however, limited to the speciiic clamp illustrated. As many clamps may be used as desired. The use of a number of clamps as distinguished from one clamp is important in equalizing the effect thereof. Assuming that the cable is to be strung for example under a final tension of 15,000 pounds, the clamp nearest the pole is first applied and properly seated and a pull exerted on the cable, say of the order of 5,000 pounds, when a slight slippage of the cable in the clamp will take place. A second clamp is then applied and a pull exerted on the cable, say or the order of 10,000 pounds, when a further slight slippage of the cable will take place. After this, a third clamp is applied and the determined maximum pull exerted on the cable. If under the last-mentioned condition, there is still a slippage of the cable, one or more additional clamps will be applied in the same manner. Because the tube I3 forms an arch support, heavy external pressure may be applied by the clamps on the steel wires without danger of injuring theinsulation 8 in any way. The compression pressure which may be applied by the clamps causes a friction between the steel wires and tubes suiiicient to resist any pull exerted by the span of cable between poles. If desired, the steel wires only may be laid over the tube I3 or both the hard and soft wires. However, where taps from the line are to be made, it will generally be desirable to clamp only the steel wires, utilizing the soft wires to form a jumper connection to the adjacent length. Where it is not considered necessary or desirable to make taps or anchor the cable, it may be carried by simple supports secured to the other poles.

The next steps to be considered are those of securing the tube I3 to the poles I5 or other supports, and getting the insulated inner conductor 1 out of the tube. As one illustration the tube may be flattened at one end to form a head I6, Fig. 4, which has an opening to receive the bolt of a clevis I1, the latter having a screw threaded bolt which passes through the post. A nut I8 on the bolt serves as a take-up means for the cable as well as a means to take the load.

To get at the inner insulated conductor 1, the tube I3 is provided with an opening I! of suitable size and shape through which the conductor extends. Desirably, the shield I2 of copper tape covers the insulation where the conductor extends through the opening I9 and covers the conductor to the joint. From Fig. 4, it will be seen that one end of the tube I3 is beveled, the purpose being to avoid sharp corners and to provide an easy change in diameter `from that of the cable proper 'to that of the tube.

When the outside wires are grounded, if it be desired to extend the cable on the other side of the pole, and also to make a tap. at the pole, the copper wires I0 instead ofl being held by the clamps are bent outward adjacent the band Il and carried toward the pole where they are united with similar wires from the left hand cable to form a jumper by the connector 2B which may be soldered to lboth of said wires. If a tap is to be made as shown in Fig. 3, a T-shaped connector isused and the copper wires I0* of the tap secured thereto, thus establishing the same potential for both the cables and the tap. The tap is supported by a tube and clamps in the same manner as the two cables. To provide for the continuity of the center conductors 1 of the two cables around the pole, the ends thereof are brought out through the openings I! as illustrated in Fig. 4 and are connected by an insulated conductor or jumper 2I, the joints thereof being covered with tape 22. It is desirable to extend the shielding tape I2 to the joints and to form it therein into a cone to reduce the electrical stresses at said joints. In the case oi a tap. the center conductor 1 thereof is brought out through the opening I9u in the tube I3i and connected by a short insulated conductor or jumper 23 to the main jumper 2 I, the joints being shielded 'and covered with insulation. terminated at a. pole, the jumpers and tap will not be used. Or a tap may be connected without the cable extending on the opposite side of the pole.

Although it is generally intended to operate the outer conductor at ground potential, it may be operated at some other potential, .for example that of the center conductor. Where this is done, the tubular clamps will be supported by the posts through string insulators as is usual in high potential installations. Y

The construction shown in Fig. 4 may be used i where it is desired to make a tap in the cable span at some point intermediate between the poles. 'I'o do this, the cable is cut at the desired point and a tube I3 mounted in each of the cable ends in the manner previously described. The heads I6 of the tubes would then be united, as shown in Fig. 7, and the conductors connected to the tap cable in the same manner as described in connection with Fig. 3. Since the tubes I3 and I3* are of metal, the outside bare wires are thereby electrically connected.

It will be seen that the tube I3 is pivotally supported at the pole, which means that it automatically accommodates itself to the sag of the span I of the cable and hence there is no undue strain tending to break it or injure the supporting wires. Also, that the arrangement provides the necessary flexibility so that any vibration of one cable is not directly imparted to the other. Also, because of the shape of the inner ends of the tube I3 and its overlying wires, the danger of the wires failing at or near the clamps is avoided. Purthermore, and which is an important factor, the supporting means are of simple construction and low in cost. A further advantage resides in the fact that the insulated center conductor or conductors are free of longitudinal strains, the load being taken entirely by the outer wires of high tensile strength.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination cables of the type each having an insulated center conductor and an outer conductor comprising bare supporting wires o! high tensile strength and bare wires of good electrical conductivity alternately and spirally arranged to form an annulus, with a tube located between the insulated conductor of each cable length and its supporting wires only. the supporting wires being spirally wrapped around the tube to increase the frietional engagement between them and the tube, individually adjustable means for clamping the supporting wires only in iirm contact with the outer wall of the tube, means securing each of the cablelengths 'to a common support and maintaining them un. F

der tension, and a jumper connected at its ends to the wires of good conductivity beyond the outer ends of the tubes to unite the conductors of good conductivity.

If the cable is to be.

2. In combination a pair of power cables, each 75 having an insulated center conductor and an outer conductor composed of interlocked hard and soft wires forming an annulus enclosing the center conductor and engaging the insulation thereon, the hard wires supporting the weight of the cable when it is suspended in service, a metal tube having a smooth outer wall inserted between the insulation on the inner conductor and the hard wires only, individually adjustable spaced clamps surrounding the hard wires only for clamping them in rm frictional contact with the outer wall of the tube, the clamps permitting limited individual slipping of the hard wires under them to equalize the tensile strains thereon when the cables are suspended, means electrically connecting the soft wires of one cable with those of the other, a jumper electrically connectuing the center conductor of one cable with that of the other, and a support to which the tubes are connected for sustaining the weight of the cable and around which the jumper passes.

3. In combination a pair of power cables of the type having each an insulated center conductor and an outer conductor of-interlocked bare wires forming a compact annulus with the wires in electrical contact, certain of the wires being hard and the remainder soft, with a metal tube having a smooth outer wall inserted between the insulation and the hard bare Wires of each cable, the tube having an opening therein with the insulated conductor extending therethrough, spaced clamps individually adjustable located on the sideof the opening adjacent the main portion of the cable for clamping only the hard bare wires in firm contact with the outer wall of the tube, the soft` wires branching outwardly from the cables adjacent the outer end of the tubes, the clamps permitting the hard Wires individually to adjust themselves by slipping under the clamps by amounts determined by the endwise pull to which they are subjected, a jumper for electrically connecting the center conductors, and means for uniting the branching ends of the soft wires.`

4, In combination a cable of the type having an insulated center conductor operating at high potential and a, bare outer conductorof interlocked alternate hard and soft bare wires forming an annulus operating at ground potential with a relatively short metal tube having a smooth external surface and a tapered outer end inserted between the insulated conductor and the bare conductor, the tube having an opening through which the insulated conductor extends, the tube also forming a support over which the hard wires are spirally Wrapped, a metallic shielding tape to prevent corona effects Wrapped around the portion of the insulated conductor within the tube and also over the portion thereof extending through the opening in the tube, and spaced clamping means individually adjustable for holding the hard Wires in firm frictional contact with the smooth external surface of the tubes, the clamps permitting the hard wires individually to adjust themselves by slipping under the vclamps by amounts depending upon the longitudinal pull thereon.

5. In combination a cable of the type having an insulated center conductor and an outer conductor comprising bare supporting hard wires of high tensile strength and relatively soft bare Wires of good electrical conductivity alternately arranged to form a compact annulus, with a relatively short metal tube having a smooth outer wall insertedV between the center insulated conductor and the bare supporting wires, the inner wall engaging the insulation, spaced clamps individually adjustable for holding the supporting wires only in rm contact with the outer wall of the tube, the clamps permitting the supporting wires individually to adjust themselves by slipping under the clamps by amounts depending upon the pull to which they are subjected, the bare wires of good conductivity branching off from the cable between it and the outer end of the A tube for electrical connection to another conductor, and means subject to tensile stress for securing the tube and cable in an elevated position 

